Effects of Alloying Elements on the Toughness and Microstructure of HIGH CURRENT DENSITY GAS SHIELDED ARC PROCESS Weld Metals

Abstract

Effects of thermal and physical properties of materials on the transient response of temperature to a step change in welding speed were investigated using TIG arc welding and FEM calculation of three-dimensional heat coduction. The materials used in this study were stainless steel, mild steel, aluminum alloy, brass and copper 9 mm in thickness.In TIG arc welding of low heat-conductive materials, large difference in maximum temperature appears in the period between former quasi-state and latter one. On the other hand, high heat-conductive materials indicate large difference in temperature gradient, but a little change in maximum temperature. In addition, the high heat-conductive materials require longer distance or time to be in latter quasi-state. The transient response from former to later quasi-state is characterized by the fraction of maximum temperature and temperature gradient to those at both quasi-states. These experimental results are confirmed by FEM calculations based on three-dimensional heat conduction. It is also clarified that although the maximum temperature mainly depend upon the thermal conductivity and thermal diffusivity, the transient response is dominated only on the thermal diffusivity. Therefore, the high thermal diffusive materials show slower response to a step change in welding speed.